Abstract A cyclotron named ARRONAX is being built in Nantes (France). It is mainly devoted to radiochemistry and nuclear medicine research and will be operational the last quarter of 2008. This machine will accelerate both protons and α-particles at high energy (up to 70 MeV) and high intensity (2 simultaneous proton beams with intensity up to 350 µA). In nuclear medicine, these characteristics will allow the cyclotron to produce a large variety of radionuclides on a regular schedule and in sufficient amount to perform clinical trials. A priority list of 12 radioisotopes, which contains isotopes for therapeutic use as well as for PET imaging, has been established by an international scientific committee. In radiochemistry, a vertical pulsed α-beam will allow fundamental studies of radiolysis in aqueous media, which is of great interest for radiobiology and for nuclear waste management.